Estimating the Per-Contact Probability of Infection by Highly Pathogenic Avian Influenza (H7N7) Virus during the 2003 Epidemic in The Netherlands
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Date
2012
Journal Title
Journal ISSN
Volume Title
Publisher
PLoS ONE
Abstract
Estimates of the per-contact probability of transmission between farms of Highly Pathogenic Avian Influenza virus of H7N7
subtype during the 2003 epidemic in the Netherlands are important for the design of better control and biosecurity
strategies. We used standardized data collected during the epidemic and a model to extract data for untraced contacts
based on the daily number of infectious farms within a given distance of a susceptible farm. With these data, we used a
maximum likelihood estimation approach to estimate the transmission probabilities by the individual contact types, both
traced and untraced. The estimated conditional probabilities, conditional on the contact originating from an infectious farm,
of virus transmission were: 0.000057 per infectious farm within 1 km per day, 0.000413 per infectious farm between 1 and
3 km per day, 0.0000895 per infectious farm between 3 and 10 km per day, 0.0011 per crisis organisation contact, 0.0414
per feed delivery contact, 0.308 per egg transport contact, 0.133 per other-professional contact and, 0.246 per rendering
contact. We validate these outcomes against literature data on virus genetic sequences for outbreak farms. These estimates
can be used to inform further studies on the role that improved biosecurity between contacts and/or contact frequency
reduction can play in eliminating between-farm spread of the virus during future epidemics. The findings also highlight the
need to; 1) understand the routes underlying the infections without traced contacts and, 2) to review whether the contacttracing
protocol is exhaustive in relation to all the farm’s day-to-day activities and practices.
Description
Keywords
Infection, Pathogenic Avian Influenza (H7N7) Virus, Epidemic
Citation
Ssematimba A, Elbers ARW, Hagenaars TJ, de Jong MCM (2012) Estimating the Per-Contact Probability of Infection by Highly Pathogenic Avian Influenza (H7N7) Virus during the 2003 Epidemic in The Netherlands. PLoS ONE 7(7): e40929. doi:10.1371/journal.pone.0040929